Field of the Invention:
This invention relates generally to tonneau covers. Specifically, the present invention is directed to obtaining an improved load bearing tonneau cover through the use of friction stir welding.
Description of Related Art:
A tonneau cover may describe a hard or soft cover used to protect unoccupied passenger seats in a convertible or roadster, or the cargo bed in a pickup truck. Hard tonneau covers may open by a hinging or folding mechanism while soft covers may open by rolling up.
A tonneau cover may be used to conceal cargo or protect cargo from the elements. When the tonneau cover is used, it may keep cargo out of the sun and provides extra security by keeping items out of sight.
Tonneau covers have been well documented in publications since their inception in the early 1900s as a means to cover or conceal cargo in a vehicle. Even though vehicles have evolved in design and function over the years, the design of marketable tonneau covers may have only evolved in terms of aesthetics rather than increased practical functionality.
The largest market for tonneau covers may be the pickup truck. It has been estimated that 98% of the tonneau covers made for this market serve the singular function of covering the cargo bed to compliment the look of the vehicle.
One style of tonneau cover is the soft cover. The soft tonneau cover may generally be made from fabrics or fabric composites that resist water and UV light damage. This may be the most common cover because of its low cost. This style may be made to retract or roll up or back into position. The soft tonneau cover may occupy the least amount of space and there are a variety of attachment and fastening methods that are employed to attach it to a pickup truck.
A second style of tonneau cover is the hard cover. The hard cover is typically made from fiberglass, hard plastic, rubber, aluminum or some combination of these or other materials. The tonneau covers made from fiberglass may be described as a single shell type cover that opens by a hinge at the cab portion of the bed. Because they are quite heavy they may include pneumatically assisted cylinders for opening and closing. The hard tonneau covers are often made to order so that their color matches the color of the truck.
A variation of the hard tonneau cover is one that utilizes a series of foldable sections to cover the cargo portion of the bed. These sections can fold together from the rear to the front of the truck and stack near the cab to make use of the cargo portion of the truck bed. A variation of this design is to have a foldable section that opens from the side of the truck bed. The hard tonneau covers may either have locks located in the foldable panels or open from the inside of the bed. Typically, the covers that open from the inside of the bed rely on the factory locking tailgate to secure the bed contents. The hard tonneau cover is the next cost increment to not only cover the contents of the truck bed but to secure them as well with a lock system so that valuable items can be safely kept in the truck bed.
Both hard and soft tonneau covers may have a profile as low as possible with the top edge of the truck bed sides and tailgate for improved aesthetics. As a result, additional hardware may be needed to mount the tonneau cover to the inside walls of the truck bed.
One style of hard tonneau cover, fabricated from aluminum, has been developed to carry a load on the top while leaving the bed under the cover to carry additional items. This cover opens in a gull-wing manner with hinges secured across the middle of the truck bed allowing aluminum sections to open in the front behind the truck cab and at the tailgate. The utility is further increased by using boat style cleats for cargo tie downs. This style of tonneau cover is locked from the top of the cover and may have a protruding handle lock.
It is important to note that tonneau covers are aftermarket purchases that may need to be aesthetically pleasing to attract customers. Also, the owner may resist modifying a vehicle by making permanent changes such as drilling into the body or bed for attachment points.
There are some problems with existing tonneau covers. The soft tonneau covers may be limited to a covering function and cannot effectively be used for supporting objects. These tonneau covers may only protect the contents of the truck bed from weather. They may require multiple fasteners to be installed on the truck bed. It is a problem for many vehicle owners to drill holes in their vehicle for mounting these fasteners. In the event that it is desired to remove the cover altogether, the vehicle is left with exposed fasteners or if the fasteners are removed, permanent holes in the vehicle.
The single section hard tonneau cover, such as those made of fiberglass, may also require hardware mounted to the bed itself. This hardware may include hinges near the cab, gas struts on the sides and some sort of locking mechanism on the tailgate. In most cases, they are special ordered to be painted the color of the truck and a professional installer may need to be used for the installation.
There are several problems with this hard tonneau cover system. For example, the single section may only be opened as far as the gas struts allow. This means that nothing higher than the bed rails (if the cover is closed) could be put in the cargo section of the bed unless the hard tonneau cover itself is removed. If the hard tonneau cover is removed, it typically requires 2 people to undo hardware and lift the cover from the truck. This additional cost along with the yearly change in bed sizes for new truck models may make this a difficult and costly manufacturing/supply process.
Another problem with this hard tonneau cover design is the use of screws to attach hardware to the truck bed. A truck may experience extreme vibration during work and recreational use, especially if it is driven off road. Over a short amount of time, the thin sheet metal surrounding the screws may have a tendency to wear, deform and enlarge leaving a heavy tonneau cover improperly secured to the vehicle.
Hard tonneau covers with folding sections may add the element of utility by folding back and allowing objects taller than the sides of the bed to be transported in the bed without removing the hard tonneau cover. Unfortunately, most of the designs for hard tonneau covers have a significant number of parts required for construction to achieve this design objective. This construction may include rails that must be attached to the inside of the bed rails and each foldable section must fit uniformly and rest on these rails.
If the inside measurement across the width of the truck bed at the tailgate is 2 to 4 inches less than the inside measurement taken across the bed at the cab (both measurements taken at rail height) as in many trucks, each folding section may need to be trapezoidal in shape for proper fit up with the bed rails. This taper varies with make, model and year, and is a tremendous difficulty and expense for manufacturers to deal with for the multitude of trapezoidal shaped folding sections.
The problem may often be managed by offshore sourcing of materials to reduce cost and followed by domestic assembly of the components. Offshore sourcing is becoming more problematic because of long lead times, higher shipping costs, and higher component costs as world manufacturing costs merge closer together. Also, the uncertainty of foreign suppliers and their respective governments, means that domestic manufacturers must bear the risk of higher inventories, and consequently, higher costs. Further, costs may be incurred as a result of obsolete products which cannot be dumped in the market place without affecting existing price levels.
For the additional cost, these folding hard tonneau covers have only added a single dimension of utility by increasing cargo bed utilization. It is unfortunate that much of the cost and effort that goes into the design and fabrication of a folding hard tonneau cover may not provide additional utility. For example, the hard tonneau cover may not be able to carry loads or objects on top without being damaged. Many hard tonneau cover designs do not allow for any load whatsoever on top and therefore do not have attachment points to carry a load. In addition, the inherent design of the hard tonneau cover may not allow any load on the top surface because of small rails that are designed only to bear the weight of the tonneau cover and not the additional cargo load.
A pickup truck bed utility might be increased if additional items or cargo could be placed on top of the hard tonneau cover and secured while maintaining aesthetics of the cover.
One prior art design tried to provide this functionality by using aluminum tread plate sheet as a top layer with square tubing welded to the underside. This design has several design problems. First, the design prevents tall bed cargo utility by allowing only a small portion of the bed to be accessible to carrying tall cargo. Second, this tonneau cover is secured in the middle section of the truck bed by connecting the truck rails directly over the wheel wells. Hinges connect a front cab facing section and rear tailgate facing section aluminum structure which partially open with gas strut assistance. This design prevents the use for cargo taller than the bed rail to be placed in the truck bed. The struts can be disconnected on one side to somewhat increase the payload capacity, however securing the payload with tie downs is severely limited. Third, the tie down method employed utilizes a series of cleats that extend above the surface around the periphery of the cover. These cleats are prone to breakage during loading and unloading and are aesthetically undesirable. Fourth, the aluminum is conventional welded throughout the entire construction of the hard tonneau cover. These welds may cause distortion, may cause solidification defects, may be a starting point for corrosion, and may be a starting locations for crack initiation—especially when the tonneau cover is under load. Fifth, conventional hinges are mechanically attached to the folding sections and may be prone to loosening. The locations may also be locations for water entry and don't protect cargo under the cover from the weather. Sixth, there are latches on the top surface that lock the cover to the truck. These latches also protrude above the surface of the hard tonneau cover and prevent loads from being slid on and off of the surface of the cover. Seventh, because this load carrying design does not allow access to much of the bed, it may need to be removed to allow the use of hitching a goose neck trailer (used for cargo, livestock hauling, etc.) and 5th wheel trailers used for recreation.
Another matter that must be discussed is a latching mechanism that needs to be used to prevent the embodiments of the invention from moving during braking or acceleration of a vehicle. It seems that there are an infinite number of latch styles and types for many applications. They range from typical door latches used in homes to specialty latches found in the automotive and aerospace applications. The majority of these applications utilize latches that restrict one degree of freedom of each side of a hinged device. Simply stated, they are used to keep two components on a hinge from opening. The next most common hinge restricts 2 degrees of freedom and is used to maintain the closure of 2 components but resists lateral sliding along the hinge axis. The most common of these latches is a buckle latch. Buckle latches are common to travel trunks that need to resist the top and bottom sections from sliding apart at the closure plane. These latches are used when the hinge is not rigid enough to prevent an extra degree of freedom.
It is interesting to note that assembly engineering design convention typically utilizes latches that resist one degree of freedom for the use of the assembly. In other words, hinges are designed to resist load conditions except for the movement of opening and closing said hinged components. This latch style resists one degree of freedom, the motion to open the hinged components. There are many design opportunities where the hinge is compliant and cannot resist all of the degrees of freedom of the hinged assembly. One example of this case is the load bearing foldable tonneau cover. Compliant hinges may be used to join at least 2 load bearing sections of this foldable tonneau cover. Since the hinges are compliant, the forces of the load secured to the top of the cover and the tonneau cover itself must be reacted against the truck bed in some fashion. This latch system must react 3 degrees of freedom—1. The force to lift the cover upwards, 2. The force to prevent the cover and load from sliding forwards when the truck brakes are suddenly applied, and 3. The force applied when the truck quickly accelerates. Each section of the tonneau cover that has an attached load must be able to react the forces to the bed of the truck. In addition, the latch system must be low profile and still allow each cover to fold on itself.
There are many other examples of assemblies and compliantly hinged components that could benefit from a latch solution that would eliminate at least 2 degrees of freedom.
It is to be understood that the following description is only exemplary of the principles of the present invention, and should not be viewed as narrowing the claims which follow.